Accelerating and braking control system



Nov. 7, 1950" D. E. 'FINDLEY 2,528,504

ACCELERATING AND BRAKING common. sysma Filed JuneilO, 1948- DONALD E F/NDLEY Patented Nov. 7, 1950 ACCELERATING AND BRAKING CONTROL SYSTEM Donald E. Findley, Alfalfa County, Okla.

Application June 10, 1948, Serial No. 32,250

1 Claim.

(Granted under the act of March 3, 1883, as amended April 30, 192 8; 370 O. G. 757) 1 This invention relates to a rotary antenna speed control system and more particularly to a system for controlling the speed of antenna electric motors of the direct current type.

An antenna as used with a radar sending and receiving set is required to be revolved about its axis so as to scan an area for radar signals, and so that the direction of said signal may be determined. As the direction is approached at which the maximum signal strength is received by the radar set, it becomes desirable to slow down the R. P. M. of the said antenna, so as not to overrun this point. This retardation is accomplished by introducing resistance in series with the armature winding of the driving motor which may, for instance, be revolving the said radar antenna at a speed of approximately 6 R. P. and so reduce this speed to 2.5 R. P. M. As this resistance is cut in by a relay switch, a second relay switch cuts in a second resistance in the armature circuit in such a manner as to effect a braking action on the speed of rotation of the armature and thereby reduce the speed more rapidly. As the armature speed drops, the voltage in the armature circuit drops and the second relay becomes deenergized to open the second resistance circuit and the speed of the armature shaft becomes constant, at a controlled low speed, maintained constant at any desired R. P. M. by means of said first resistance.

The principal object of this invention is the provision of a speed control circuit for slowing down the speed of rotation of a radar antenna.

Another object of this invention is to provide a control circuit for slowing down the rotation of antenna for a fraction of a scan to prevent a target from appearing repeatedly in the nulls of the antenna pattern.

A further object of this invention is to change the speed of a D. C. electric motor used for the rotation of an antenna by the introduction of a resistance in series with said motors armature circuit.

A still further object of this invention is to introduce a second resistance in said armature circuit, which will set up a braking force to quickly retard the rotation of said armature to some predetermined speed of rotation.

A final object of this invention is to have an adjustable potentiometer in a D. C. motor armature circuit, so that a selective low speed of said motor can be maintained after a braking action has been released. I 1

These and other objects of this invention and the various features and details of the construction, operation and use thereof, are hereinafter more fully set forth and described with reference to the accompanying drawing, in which:

The figure shown is a diagrammatic view of the electrical circuits and connections comprising this invention.

Referring now to the drawing, numeral l designates the armature of the D. C. motor which revolves the antenna (not shown), and '2 designates a terminal block for connecting the various circuits involved. Switch 3 connects the terminal block 2 to the positive side of the power source, wires 4 connect to the two armature brushes and wire 5 connects the terminal block 2 through anantenna control switch (not shown) to the negative side of the power source. Wire 6 connects terminal block 2 through the series field winding of the motor to the positive side of the power source. Wire 1 connects switch 3 through terminal block 2 to one end of a relay 8 operating switch 5; and from the other end of said relay 3 a wire 9 connects to the negative side of the power source through terminal block 2 and wire 5.

A relay H] is connected at one end to one of the wires 4 through terminal block 2 and at the other end to normally open stationary contact l5 of relay 8 through variable resistance l3 and wire I4. Resistance !2 is connected at one end to the first-mentioned end of relay [0 and at the other end to the other normally open stationary contact of relay 8 through the normally open contacts ll of relay iii and through lead 18. A variable resistor I! is connected at one end through lead it to the other of the wires 4' and at the other end through wire Hi to one normally closed contact of relay 8, said contact being connected to wire 6 at the terminal block 2 by means of g The movable contacts of relay 3 are 4 and I9, upper wire 4 and the armature to the negative side of the source and the motor operates in a normal manner. When it is desired to decrease the speed of the motor switch 3 is closed thereb energizing relay 8 through leads 5, I and. 9,. When relay 8 is energized the series circuit through the armature l and the series field winding is broken, and a new circuit, including armature i, upper wire 4, wire l9, variable resistance ll, wire I6, wire 2|, wire 6 and the series field winding, is completed thereby connecting resistance H in series with armature l.

Furthermore, when relay 8 is energized, relay 10 becomes energized, closing contacts H and connecting resistance 12 in parallel with the armature across wires l thereby producing a braking action on the rotation of said armature so as to rapidly reduce its speed. As the speed of armature I drops, the voltage across relay 10 drops until the relay i0 is deenergized and contacts it open. After this braking action is removed the slow speed is then controlled by resistor i'l. Resistance 53 and relay iii are across the armature at all times during the armatures slow speed operation and the length of time for the operation of the electric brake (resistance 12) depends, therefore, on the adjustment of resist ance Hi. It was found that with the slow speed set forth above, the braking action caused the antenna to stop and reverse, thereby making sector scan possible.

While a particular embodiment of this invention has been illus rated and described herein, it is not intended that this invention be limited to such disclosure, and changes and modifications may be made and incorporated Within the scope of the claim.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

A speed control system for an electric motor having an armature, said system comprising: a resistive element; first relay means for connecting said element across said armature; a variable impedance; second relay means selectively energizable for simultaneously inserting said imped ance in series with said armature and connecting said first relay means across said armature to thereby energize said first relay means, said first relay means being deactuated when the speed of saidarmature decreases to a predetermined value; and adjusting means connected to said first relay means to control the point of deactuation thereof. DONALD E. FINDLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,016,470 Barnum Feb. 6, 1912 1,064,809 Barnum June 17, 1913 1,122,259 Cummiskey Dec. 29, 1914. 

